The present invention relates to fuel control systems and, particularly, relates to fuel control systems for gas turbines.
Industrial and power generation gas turbines each include a combustion system that provides fuel, e.g., gas and or liquid fuel, to combustors. In a gas turbine, a fuel control system regulates the amount of fuel that is provided to fuel nozzles in the combustors. Fuel control systems typically include programmable logic circuits, such as computers or microcontrollers, that determine appropriate rate of fuel flow or pressures of the fuel flow to the fuel nozzles. These logic circuits may monitor the fuel flow rate and pressure, and other parameters of the combustion system in the gas turbine. These logic circuits dynamically adjust fuel control valves to maintain a desired fuel flow or pressure to the fuel nozzles.
Fuel control systems are intended to maintain a stable flow of fuel to the combustors over the entire operating range of the gas turbine. It is known to monitor the fuel pressure at the fuel nozzle and apply the fuel pressure as feedback to regulate the flow of fuel to a combustor. A conventional fuel controller, such as described in U.S. Patent Application Publication 2007/0157,619, has a proportional-integral (PI) control algorithm having a PI control gain applied to a fuel pressure feedback signal to maintain a constant fuel pressure to the fuel nozzles in a combustion system.
Undesired oscillation of fuel pressure and fuel flow and other undesired conditions of the fuel flow can result with conventional fuel controllers that include PI control algorithms. The oscillations in fuel pressure and flow may disrupt the operation of the combustion system. There is a long felt need to eliminate or at least reduce undesirable pressure oscillations in the fuel flow to the combustion system in an industrial gas turbine.